The present invention relates to a small-size motor and, more particularly, to a small-size motor capable of being directly fitted with electric elements such as capacitors for driving electrical equipment, household electrical appliances, or the like.
A small-size motor used for driving electrical equipment, household electrical appliances, or the like is desired to be directly fitted with electric elements such as a capacitor, a diode, and a choke coil, in a motor case cover made of synthetic resin. For example, chip capacitors are attached to reduce electrical noise. However, the case cover of the conventional small-size motor has an insufficient space for installing a required number of electric elements.
FIG. 6 is a view of a case cover of a small-size motor having a conventional construction, which is viewed from the inside of the motor (see Japanese Utility Model Application Laid-Open No. 4-121384). FIG. 7 is a partially sectional view of the case cover shown in FIG. 6, in which the case cover is cut at a capacitor portion. In FIGS. 6 and 7, a case cover 11 made of synthetic resin is provided with a pair of input terminals 26 and a pair of brush arms 12. Each of carbon brushes 4 is fixed respectively at a free end of the brush arm 12 connected electrically to the input terminal 26.
Each of a pair of capacitors 15 is inserted in a void formed in the case cover 11. An electrode 27 on one side of the capacitor 15 is in contact with the extension 26a of the input terminal 26, and on the other hand, a substantially U-shaped spring member 25 is in contact with an electrode 28 on the other side of the capacitor 15. Thus, not only electrical connection can be ensured, but also the capacitors 15 can be fixed firmly in a void in the case cover 11 by being pressed transversely. The spring member 25 also can ensure electrical connection with a metallic case when the case cover 11 is fitted to the case.
By the capacitor installation construction as shown in the figures, the need for soldering work and lay-out work for connection wires, which necessarily accompany the connection work for electric elements, can be eliminated. Thus, the electric elements such as capacitors are securely fixed in a limited space, and on the other hand, electrical connection can be provided with high reliability. However, although two electric elements can be installed in the case cover by the construction shown in the figures, three electric elements cannot be installed.
FIG. 8 is a view for illustrating the need for installing three electric elements. FIG. 8(A) is a schematic electrical connection diagram for a small-size motor having a conventional construction as shown in FIG. 6. In FIG. 8, reference character M denotes a motor, and C1 to C3 denote capacitors. A power source is connected to rotor windings of the motor M via brushes from the input terminals, and also is connected respectively to one electrode of each of the two capacitors C1 and C2. The other electrodes of the two capacitors C1 and C2 are connected to each other, and grounded to the metallic case of the motor from the connection point. In the conventional configuration shown in FIG. 8(A), since only two capacitors C1 and C2 can be installed, the configuration as shown in the FIG. 8(A) is unwillingly adopted, and therefore the electrical noise reducing effect is insufficient on the low-frequency band.
Contrarily, if three capacitors can be installed to provide electrical connection, the wiring can be accomplished as shown in FIG. 8(B). Specifically, in addition to the wiring shown in FIG. 8(A), a third capacitor C3 can be connected across both input terminals. It has been known that such a circuit is superior in terms of the electrical noise reducing effect on the low-frequency band.
Accordingly, an object of the present invention is to provide a small-size motor in which a sufficient space is secured in a motor case cover made of synthetic resin so that three electric elements such as chip capacitors can be incorporated together with their wiring and support arrangement.
The small-size motor in accordance with the present invention includes a metallic case 1 having a bottomed hollow cylindrical shape, fitted with a magnet 2 on the inner peripheral surface thereof; a case cover 11 made of synthetic resin, mounted so as to close an opening of the case 1; and a rotor fitted with a laminated core 22, windings 23 wound on the laminated core 22, and a commutator 24 on a shaft 21. The case cover 11 supports a pair of brush units each of which has a brush arm 12 fitted with a brush 4 and a brush base 13 fixed and connected to the brush arm 12. The case cover 11 is formed with three voids to contain three electric elements such as chip capacitors. A first electric element is fixed mechanically between the paired brush units in a first void to be connected electrically. The remaining two second and third electric elements are located on both sides of the first electric element and are pressed on the brush base in the motor shaft direction by a body earth terminal 14 in second and third voids, so that the body earth terminal 14 is fixed to the case cover 11, whereby the two electric elements are fixed mechanically and connected electrically.
Also, the first electric element is fixed mechanically and connected electrically between both fixing portions 8 via a metallic spring (U-shaped spring 18), each of which connects the brush arm 12 of each of the paired brush units with the brush base 13. One electrode of each of the second and third electric elements is mounted on the side face of a brush base end portion 9, and the other electrode thereof is pressed by the body earth terminal 14.
Further, the body earth terminal 14, which is formed by being stamped out of a metal plate and being bent, includes an element pressing portion 16 for pressing the electric element, a body earth portion 17, and a holding portion 20, and is installed so as to cover a case cover fitting portion 7 fitted to the case 1 in such a manner that the case cover fitting portion 7 is held by the body earth portion 17 from the outside and by the holding portion 20 from the inside.
Thus, three electric elements such as chip capacitors can be incorporated together with their wiring and support arrangement.